Properties of paper mill sludge–wood fiber–HDPE composites after exposure to xenon-arc weathering

We used paper mill sludge（PMS） to substitute for part of the wood fibers（WF） used to reinforce high density polyethylene（HDPE）.The resulting composites were subjected to xenon-arc weathering.The composite filled with limited PMS（under 10 %） had mechanical properties and aging resistance similar to those without PMS.The composites containing more PMS faded and cracked more readily than those without PMS.Based on the carbonyl index,crystallinity,and wood index,PMS appeared to accelerate the degradation of composites during weathering.Adding PMS to WF–HDPE composites reduced the weathering resistance,and this reduction was not significant if the PMS content did not exceed 20 % of the wood fibers.Therefore,PMS could be used as a reinforcement in wood-plastic composites at levels less than20 % of the wood fiber content.

Printability of HDPE/Natural Fiber Composites with High Content of Cellulosic Industrial Waste

In this paper, a continuous polymeric matrix highly filled with fiber of sugarcane bagasse has been obtained and its feasibility as an ink-absorbing material has been evaluated. In order to study the effect of the amount of cellulose fiber on the surface printability, contact angle measurement using different liquids—water-based inks, ethanol and ink for ink-jet printers—and printing tests were performed on composites of high density polyethylene (HDPE) and sugarcane bagasse (SCB). The composites were processed in a Haake internal mixer, using the SCB without any previous chemical treatment or compatibilizer. The differential scanning calorimetry (DSC) and derivative thermogravimetry (TG/ DTG) revealed an increase in the thermal stability and in the degree of crystallinity of the HDPE. The optical microscopy (OM) and scanning electron microscopy (SEM) showed that the cellulosic material was homogeneously embedded within the HDPE matrix. In order to assess the resistance of the composite sample to the pull strength of the printer, tensile tests were applied to the composites and the results were compared to known paper samples. The best result was achieved in the composite with the highest content of SCB, as well as the shortest drying time.

紫外线辐照HDPE\PVA短纤维共混物相容性及力学性能的研究

采用接触角测定、ＳＥＭ、抽滤分析和力学性能的测试研究了紫外线辐照ＨＤＰＥ＼ＰＶＡ短纤维共混物的力学性能和相容性。结果表明，经紫外线辐照后，由于在分子链上引入了＞Ｃ＝Ｏ、－ＣＯＯＨ、－ＯＨ等极性基团，ＨＤＰＥ与水的接触角变小，亲水性增加。在与ＰＶＡ短纤维共混过程中，ＨＤＰＥ分子链上引入的含氧基团与ＰＶＡ分子链上－ＯＨ基团形成氢键，增强了共混体系相界面相互作用，使共混物的拉伸强度和冲击强度得到了明显提高。当辐照时间超过１４４ｈ，由于ＨＤＰＥ降解严重，共混物的韧性突降。

HDPE紫外辐照改性及其与PVA共混体系的力学性能

研究了紫外辐照对高密度聚乙烯（ＨＤＰＥ）结构与性能以及ＨＤＰＥ／聚乙烯醇（ＰＶＡ）短纤 维共混体系力学性能的影响．结果表明，在空气中通过紫外辐照可在ＨＤＰＥ分子链上引入Ｃ＝Ｏ、Ｃ—Ｏ 含氧基团，使ＨＤＰＥ分子量下降、熔点降低、结晶度增大并产生凝胶．以辐照ＨＤＰＥ为增容剂，增强 了ＨＤＰＥ与ＰＶＡ相界面的相互作用，共混物的拉伸屈服强度和缺口冲击强度得到提高．

配筋PVA-钢混杂纤维增强水泥基复合材料梁柱边节点抗震性能试验研究

改善工程材料韧性和耐久性,提高框架梁柱节点抵抗变形和破坏的能力,是提高框架结构抗震韧性的有效途径之一。采用PVA-钢混杂纤维增强水泥基复合材料代替普通混凝土应用到梁柱边节点,考虑轴压比和加密区体积配箍率的影响,设计6个配筋PVA-钢混杂纤维增强水泥基复合材料、1个配筋单掺PVA纤维增强水泥基复合材料和1个钢筋混凝土梁柱边节点试件进行拟静力试验,分析其破坏形态、滞回曲线、骨架曲线、延性、耗能能力、钢筋应变和梁端塑性铰区转角,探讨混杂纤维的加入对梁柱边节点抗震性能的影响。结果表明:与钢筋混凝土节点和单掺PVA纤维增强水泥基复合材料节点相比,PVA-钢混杂纤维增强水泥基复合材料节点的承载力高、变形能力大、延性好、耗能能力强,抗震性能显著提升。当试验轴压比从0.12增加到0.24,梁端塑性铰区产生一定的外移,塑性性能发挥更充分,同时试件的变形能力、延性、耗能能力增加。在加密区体积配箍率减小的情况下,试件仍表现出良好的抗震性能。

PVA/HDPE/HDPE-g-MAH共混物的相形貌与动态流变性能

采用熔融共混法制备了聚乙烯醇（PVA）/高密度聚乙烯（HDPE）共混物,引入马来酸酐接枝高密度聚乙烯（HDPE-g-MAH）对体系进行增容。利用SEM、小振幅震荡剪切、溶剂提取、拉伸测试考察组成和增容剂含量对共混物相形貌、动态流变性质、相连续性和力学性能的影响。结果表明,当HDPE质量分数达到20%~30%时,PVA/HDPE/HDPE-g-MAH共混物呈现接近共连续的结构;储能模量-频率图中观察到较为明显的第二平台;PVA相的连续度达到98%;共混物的断裂伸长率由5%显著提高到25%左右。另外,当HDPE-g-MAH的含量增大时,共混物的相界面变得模糊,力学性能也随之提高。

PVA/CS多孔复合材料的制备及其对甲基橙的吸附性能研究

现阶段随着印染行业迅速发展,在为大众提供更多选择的同时,也导致污染问题日益严重。印染行业生产过程中,不可避免使用颜料和染料为其产品上色,此过程中会有污染物产生。目前,关于染料治理的研究得到重点关注。本文以聚乙烯醇/壳聚糖(PVA/CS)这一多孔复合材料为基础,探究该材料制备工艺,并通过实验,证明其对酸性染料的吸附性能。最终结果表明:制备的PVA/CS多孔复合材料,具备吸附酸性染料的功能,尤其是吸附甲基橙这一纺织工业常用染料效果良好。

PVA纤维对复合改性再生混凝土力学性能的影响

为明确聚乙烯醇(PVA)纤维体积掺量和长度,以及硅酸钠和硅烷复合改性再生骨料对再生混凝土力学性能的影响,通过对6组不同纤维体积掺量、长度的组合及两组对照组试件进行力学试验,并对试验结果进行了方差分析。结果表明:硅烷和硅酸钠复合改性再生骨料和PVA纤维均能有效提升再生混凝土的力学性能,改性后的再生混凝土力学性能较改性前有显著提高。当掺入的PVA纤维体积掺量为0.1%、长度为9 mm时,再生混凝土的力学性能达到最佳。通过观察劈裂抗拉破坏后裂缝的表观形态,发现长度为12 mm的PVA纤维在抑制裂缝延伸与扩展方面表现出更好的效果。通过SPSS软件进行方差分析,发现纤维体积掺量是影响再生混凝土力学性能的主要因素。

RTP-PVA混杂纤维的工程水泥基复合材料干缩性能试验研究

为研究回收轮胎聚合物(recycled tyre polymer,RTP)和聚乙烯醇(polyvinyl alcohol,PVA)混杂纤维对工程水泥基复合材料(engineered cementitious composites,ECC)干缩性能的影响,对RTP-PVA混杂纤维总体积分数为2.0%的ECC进行流动性、直接拉伸和干缩试验,并分析混杂纤维作用机理和干缩计算模型.结果表明:RTP纤维替代率为12.5%~50%对ECC流动性影响不大,比单掺PVA纤维的ECC流动性降低1.09%~3.69%.ECC的抗拉强度随RTP纤维替代率的增加而降低,不同比例的混杂纤维比单掺PVA纤维的ECC抗拉强度降低了23.6%~56.6%.不同比例混杂纤维ECC干缩率曲线趋势相近,7 d时干缩率为28 d时的80.92%~82.77%.ECC的干缩率随RTP纤维替代率的增加而降低,28 d时不同RTP纤维替代率的混杂纤维比单掺PVA纤维的ECC干缩率降低了0.80%~2.09%.RTP-PVA混杂纤维可在ECC中协同发挥作用抑制基体干缩,结合试验结果得到适合RTP-PVA混杂纤维ECC的指数型干缩预测模型.

Fabrication of high-performance PVA/PAN composite pervaporation membranes crosslinked by PMDA for wastewater desalination

The pyromellitic dianhydride（PMDA） crosslinked poly（vinyl alcohol）（PVA） was coated on top of the PAN ultrafiltration membrane to form a PVA/PAN composite PV membranes for wastewater desalination. The composite membranes have high application value in industrial wastewater treatment. By varying the membrane fabrication parameters including the weight percent（wt%） of the PMDA, the crosslink temperature and duration, membrane with the best desalination performance was obtained. The composite membrane with a 2-lm-thick PVA selective layer containing 20 wt% of PMDA and being crosslinked at 100 °C for 2 h showed the highest Na Cl rejection of 99.98% with a water flux of 32.26 L/（m^2 h）at 70 °C using the 35,000 ppm Na Cl aqueous solution as feed. FTIR spectroscopy, wide-angle X-ray diffraction, thermogravimetric analysis and scanning electron microscope have been used to characterize the structures and properties of both the crosslinked PVA dense films and PVA/PAN composite membranes. The effects of the concentrations of PMDA,the crosslinking time and temperature to the membrane water contact angle, swelling degree, salt rejection and water flux were systematically studied.

Tensile properties of strain-hardening cementitious composites containing polyvinyl-alcohol fibers hybridized with polypropylene fibers

Partially replacing polyvinyl-alcohol(PVA)fibers with polypropylene(PP)fibers in strain-hardening cementitious composites(fiber hybridization)modify certain mechanical properties of these materials.The hybridization based on the introduction of low-modulus hydrophobic polypropylene fibers improves the ductility and the strain-hardening behavior of the cementitious composites containing polyvinyl-alcohol fibers of different types(PVA-SHCC).Pull-out tests indicate that adding PP fibers increases the energy capacity of the hybrid composite with respect to the material containing only PVA fibers under tensile loading,and PP-fiber geometry(i.e.,section shape and length)is a key factor in enhancing the strain capacity.

Synthesis and Characterization of Polymeric Composites Embeded with Silver Nanoparticles

Silver nanoparticles were synthesized by chemical reduction method. The Ag nanoparticles (AgNP) were characterized using UV-Vis spectroscopy which shows an absorption band at 420 nm confirming the formation of nanoparticles. For any practical application of the silver nanoparticles it is necessary to stabilize it which can be done by making a composite. In the present studies three polymers were chosen such that AgNP could be put to some practical use. Polyvinyl Alcohol (PVA), Polypyrrole (Ppy) and Carboxymethyl cellulose (CMC) are important for use in textiles, electronics and food/drug technologies respectively. Polymeric composites of PVA, PPy, and CMC were prepared by mixing the aqueous solutions of the respective polymers and the colloidal suspension of preformed silver nanoparticles. Various compositions containing 1% to 5% of Ag nanoparticles were prepared. Thin films of these composites were characterized by UV-Vis spectroscopy, X-ray diffraction and Scanning electron microscopy. X-ray diffraction showed the presence of the peaks at 2θ values of 38.1°, 44.2°, 64.4 and 78.2° corresponding to cubic phase of silver metal. SEM photographs revealed the presence of Ag nanoparticles of sizes varying from 40 to 80 nm. The electrical conductivity of these materials was studied using the four probe method. The conductivity was found to increase from 10–6 for control samples to 10–3 S/cm after the formation of the nanocomposites.

The effect of Poly-ethylene-co-glycidyl methacrylate efficiency and clay platelets on thermal and rheological properties of wood polyethylene composites.

Global ecological concerns have resulted in an interest in renewable natural materials. Composites based on high density polyethylene (HDPE), wood fiber (Veneer) and containing coupling agents like nanoclay (NC) and poly-ethylene-co-glycidyl methacrylate (PEGMA) were made by melt compounding and then injection molding. In this study, the effects of two variable parameters namely nanoclay and coupling agent on the rheological and thermal properties of wood polyethylene composites (WPECs) were investigated. The study investigates the morphology phase, rheology behaviors and thermal properties by scanning electron microscope, capillary rheometer and thermal gravimetric analyzer. The SEM micrographs of the composites showed that the outer surfaces of the wood were coated by a section of amorphous lignin. The state of dispersion in HDPE/pine/clay composites was improved by EGMA because it could interact with pine flour in addition to clay. The interaction of reinforcement with coupling agent and HDPE matrix is strong based on the observation of the fracture surface of composites when EGMA is present. However the addition of 2.5% clay slightly lowered the initial degradation temperature (Td) but did not improve the thermal stability. Obviously, all the composites materials exhibit viscoelastic values greater than those of neat HDPE.

钢-PVA混杂纤维增强水泥基复合材料永久模板叠合RC单向板短期刚度计算方法

钢-PVA混杂纤维增强水泥基复合材料(HFRCC)具有良好的受拉韧性和耐久性能,是永久模板的理想材料。首先探究了PVA纤维掺量对HFRCC工作性能和抗折强度的影响,随着PVA纤维掺量增加,HFRCC的工作性能显著减弱,抗折强度先增大再减小,最终选用含有1.5%钢纤维和0.25%PVA纤维的HFRCC来制作永久模板。随后对六个HFRCC永久模板叠合RC单向板和一个RC单向板进行了四点受弯试验,探究了HFRCC-RC界面处理方式和配筋率对叠合板受弯性能的影响。试验结果表明:抹平、等距凹槽和钢钉拉毛三种界面处理方式对叠合板受弯性能的影响可以忽略;HFRCC模板能够有效限制裂缝发展,减小裂缝宽度和间距,叠合板的开裂弯矩相比于普通混凝土板提高了20.1%~31.7%。分别采用刚度解析法和有效惯性矩法建立了HFRCC-RC叠合板短期刚度计算方法,两种方法均有较高的计算精度且离散性较小。

Model of Coherent Interface Formation in Cement-Based Composites Containing Polyblend of Poly vinyl Alcohol and Methylcellulose

The texture of interfacial zone between cement paste and quartz in the cement-based composites containing polyvinyl alcohol (PVA), methylcellulose (MC) and their potyblend in an amount of 10 wt % with respect to cement, as well as the texture of dehydrated bodies of PVA, MC, and the potyblend solutions, were investigated with SEM. The network texture of the dehydrated polyblend is confirmed by comparing the texture of dehydrated bodies of PVA and MC. The network texture has restrained the movement of polyblend molecules in the cement mortar but is helpful to forming a coherent interface between cement paste and quartz. The key factor of forming the coherent interface is not the neutralization reaction between H + from hydrolysis of quarts: and OH- from hydration of cement, but the electrostatic attraction and the chemical reaction between polar groups on the polyblend molecule and cations and onions from hydrolysis of quartz and hydration of cement, respectively. The model of the coherent interface formation is that excessive [HSiO3]- and [SiO3]2- onions are bonded with the hydrated cations such as Ca2+ and Al3+ , which is confirmed by the gel containing Ca and Si on the quartz surface.

Preparation and Characterization of Nano-hydroxyapatite/polyvinyl Alcohol Gel Composites

Nano-hydroxyapatite reinforced poly（vinyl alcohol） gel（nano-HA/PVA gel） composites has been proposed as a promising biomaterial,especially used as an articular cartilage repair biomaterial.In this paper,nano-HA/PVA gel composite was prepared by in situ synthesis method and incorporation with freeze-thaw cycle process.The microstructure and morphology were investigated by X-ray diffraction,TEM,SEM and FTIR.The results showed that the size of HA particles synthesized in PVA solution was on the nanometer scale.Both the size and crystallinity of HA particles synthesized in PVA solution decreased compared with that of HA synthesized in distilled water.The nano-HA particles were distributed in PVA matrix uniformly due to the effect of PVA solution as a dispersant while low content of HA particles in the composites.On the contrary,with high content of nano-HA particles in the composites,the particles tended to aggregate.The result of FT-IR analysis indicated that the chemical bond between nano-HA particles and PVA matrix existed.The conformation and degree of tacticity of PVA molecule changed because of the addition of HA particles.Furthermore,the interfacial strength of the composites was improved due to the interaction between nano-HA particle and PVA matrix and this was beneficial to improving the mechanical properties of the composites.

Improvement of Mechanical,Dynamic-Mechanical and Thermal Properties for Noil Ramie Fiber Reinforced Polyethylene Composites

Noil discarded fibers from fiber production for textile industry have short length and are always considered less valuable.Here,noil ramie fibers/HDPE composite is prepared using twin-screw extruder and the dynamic mechanical and thermal properties are studied.The influence of ramie fiber and maleic anhydride-grafted polyolefin(MA-g-PO)on mechanical,dynamic mechanical and thermal properties is investigated.It is observed that the tensile,flexural and impact properties of the composites treated with MA-g-PO are all improved in comparison to the untreated composites.Dynamic mechanical properties of the composite with MA-g-PO show an increase in the storage modulus with a higherαrelaxation peak,together with the micromorphology analysis,indicating an improved interfacial bonding between fiber and matrix by the MA-g-PO addition.Furthermore,the change in TGA thermograms of composite caused by MA-g-PO exhibits that the addition of MA-g-PO is also helpful to increase the thermal stability of noil ramie fiber/HDPE composites.

Sodium alginate-polyvinyl alcohol/polysulfone (SA-PVA/PSF) hollow fiber composite pervaporation membrane for dehydration of ethanol-water solution

Using polysulfone （PSF） hollow fiber ultrafiltration membranes as the substrate, sodium alginate （SA） and polyvinyl alcohol （PVA） blend solutions as the coating solution, and maleic anhydride （MAC） as the cross-linked agent, SAPVA/PSF hollow fiber composite membranes were prepared for the dehydration of ethanol-water. The effects of different sodium alginate concentration in the coating solutions and different operating temperatures on pervaporation performance were investigated. The experimental results showed that pervaporation performance of the SA-PVA/PSF composite membranes for ethanol-water solution exhibited a high separation factor although they had a relatively low permeation flux. As SA concentration in SA-PVA coating solution was 66.7% and the operating temperature was 40 ℃, SA-PVA/PSF hollow fiber composite membrane （PS4） had a separation factor of 886 and flux of 12.6 g/（m^2·h）. Besides, SA-PVA/PSF hollow fiber composite membranes （PS3 and PS4） were used for the investigation of the effect of ethanol concentration in the feed solution on pervaporation performance.

PVA纤维长度对水泥基复合材料抗拉强度的影响

为了研究PVA纤维长度对水泥基复合材料抗拉强度的影响,采用6 mm、9 mm和18 mm的PVA纤维结合新疆本地沙漠砂与粉煤灰制备PVA-沙漠砂水泥基复合材料,于恒温条件养护28 d后测试其抗拉强度并与普通混凝土试件进行对比。由试验得出:添加PVA纤维的水泥基复合材料相比于普通混凝土试件其抗拉强度显著提高;随着纤维长度的增加,PVA-沙漠砂水泥基复合材料的流动度和抗拉强度逐渐降低。